The Second Schleswig War was fought in the spring and summer of 1864, over the status of the two duchies of Schleswig and Holstein. The war pitted Prussia and Austria against Denmark, and though it lasted less than three months, it still saw all of Jutland falling to the invaders and the Danish clinging on for dear life in the islands before war's end.

Note: Although it's teachnically a SoaP map, this is largely OTL, save for a few date changes. So if you all want to, you're free to use it for your presentations/essays/whatever, so long as you abide by the rules of the Creative Commons licence (AT-NC-SA)

The German Confederation included major parts of German-speaking Austria. Also the casus belli for the war was that Denmark had broken the London Protocol to which Austria was a signatory.Furthermore considering the rivalry for the leadership of the German nation between Prussia and Austria the Austrians had to go to war to further the cause of German unity in order not to fall behind Prussia.